Systems are known which are used to detect the state or instantaneous position of a gear box. Such known systems use electrical limit contactors which are intended to detect the position of each of the sliding rods which carry the gear control forks.
These known systems have various drawbacks, in particular:
A. Since each sliding rod is likely to have three positions, to wit, two end positions of engaged gear and one central position of neutral gear, it is necessary to provide at least three electric contactors on each rod. This leads to provide, for instance, fourteen contactors on an eight-speed gear box, or twenty-one contactors on a fourteen-speed gear box. It will be readily understood that such a great number of contactors makes the gear box expensive, fragile, difficult to keep in good order, and exposed or subject to frequent failures.
B. Since each contactor must be set by the corresponding rod, the workshop manufacturing the gear boxes is led to deal both with mechanical parts and electric micro-switches; since these two operations require normally quite differently qualified workers, it is not very convenient to group them in the same shop.
C. The gear box must have been wholly designed in a special way, so that it is not possible to equip existing boxes.
The object of the present invention is to obviate such drawbacks by providing a simple and inexpensive device which is readily added to gear boxes of a standard type in an independent shop.